Dzhokhar Tsarnaev’s posts are distinctive only in their utter ordinariness — ordinariness that stands in such startling contrast to the horror of what happened last week in Boston.

AP

Tamerlan Tsarnaev posted YouTube links, prophesies.

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It is America’s first fully interactive national tragedy of the social-media age.

The Boston Marathon bombings quickly turned into an Internet mystery that sent a horde of amateur sleuths surging onto the Web in a search for clues to the suspects’ identity.

And once the search focused on Tamerlan and Dzhokhar Tsarnaev, the brother’s social-media postings provided a rich vein of material to mine and sift.

There are more than a thousand messages on Dzhokhar’s Twitter account in addition to a profile page on VKontakte, a popular Russian social-networking site; and in Tamerlan’s case, a list of favorite videos on YouTube and what appears to be an Amazon wish list belonging to him (Amazon would not confirm whose list it was, citing its privacy policy).

These posts instantly became dots that people began trying to connect. Some details ratified the views of those former friends and neighbors who said they were utterly shocked at the brothers’ possible involvement in such a horrifying crime.

Other posts pointed to Tamerlan Tsarnaev’s growing interest in Islamic radicalism and possibly a dark subtext to the friendly, boy-next-door affect of Dzhokhar.

At the same time, they were reminders of the complexities of online identity — of the ways in which individuals strike poses and don masks on the Web (which can sometimes turn into self-fulfilling prophecies), and the ways in which the Web can magnify or accelerate users’ interests and preoccupations.

The younger brother Dzhokhar, in particular, seemed utterly immersed in American pop culture, and concerned with the sorts of things that preoccupy many young men — girls (“miss u.s.a. is so sexy”) and good times (“I am the best beer pong player in Cambridge. I am the #truth”).

In fact, much of his Twitter feed is distinctive only in its utter ordinariness — ordinariness that stands in such startling contrast to the horror of what happened last week in Boston.

There are lots of references to musicians like Chris Brown, Jay-Z and Michael Jackson; television shows like “Breaking Bad” and “Game of Thrones” and movies like “Spider-Man” and “Finding Nemo.” He prattles away about Nutella and Frosted Flakes, complains about typos and losing his remote. “Pop-up adds are the worst, on par with mosquitoes,” he tweeted on June 17, 2012.

Given the layers of irony, sarcasm and joking often employed on Twitter, it can be difficult to parse the messages of a stranger.

Yet some of them can seem menacing or portentous, given what we now suspect: “a decade in america already, I want out,” “Never underestimate the rebel with a cause,” or, “No one is really violent until they’re with the homies.”

But others suggest a more Holden Caulfield-like adolescent alienation: “some people are just misunderstood by the world thus the increase of suicide rates.”

Sometimes, Dzhokhar sounds downright sentimental (unless, of course, he is being ironic): “There are enough worms for all the birds stop killing each other for ‘em.”

Parts of Dzhokhar’s VKontakte page are harsher and more serious. Under personal priority, it says “Career and money.” Under world view, it says “Islam.”

There is a link to a video indicating outrage at the violence in Syria, and a link to an Islamic website that says, “And do good, for Allah loves those who do good.” Another video features a blind boy talking to an older man, saying he believes his blindness will be absolved on Judgment Day; the man starts to cry, and wonders how many people who have their sight are as committed to the study of the Quran as the boy.

Other posts on Dzhokhar’s page have a more sardonic edge. There is a link to a self-described “journal of sarcasm” called “Evil Corporation” (featuring a logo reminiscent of Angry Birds) and also a joke that goes like this: “A car goes by with a Chechen, a Dagestani and an Ingush inside. Question: who is driving? The answer: the police.”

The videos linked to on Tamerlan’s YouTube page — which was created in August 2012, shortly after a trip to Russia — are far more militant, and hint at a growing radicalization on his part. About seven months ago, he posted a couple of videos of Timur Mucuraev, whom The Washington Post has described as “the bard of Chechen separatism.”

Five months ago, he posted a video (subsequently deleted) under the subhead “Terrorists.” The video, CNN has reported, featured a militant named Abu Dujana (aka Gadzhimurad Dolgatov), who was killed by Russian security services in December. The video reportedly shows the leader in sunglasses, flanked by two others, their faces hidden by balaclavas, brandishing automatic weapons.

Four months ago, a link went up on Tamerlan’s YouTube page to a video called “The Emergence of Prophecy: The Black Flags from Khorasan.” The black flags refer to a kind of Armageddon-like prophecy reportedly embraced by al-Qaida — about jihadis rising up from Central Asia to defeat the infidels.

A video link featuring the radical Islamic preacher Feiz Muhammad has been removed from the YouTube site in the past several days; it featured the preacher denouncing Harry Potter as glorifying “paganism and evil” and teaching “children the drinking of unicorn blood and magic.”

As for what appears to be Tamerlan Tsarnaev’s Amazon wish list page, it is a weird jumble of self-help books (Dale Carnegie’s “How to Win Friends and Influence People”), covert-operations-style manuals (“The I.D. Forger: Homemade Birth Certificates and Other Documents Explained”), Chechen history books (“Allah’s Mountains: The Battle for Chechnya, New Edition”), Mafia books (Nicholas Pileggi’s “Wiseguy”) and books about the Roman Empire (“The Decline and Fall of the Roman Empire”).

There is also Boethius’ “Consolation of Philosophy” — a staple of college curriculums that addresses notions of good and evil and free will — and “Snatch,” the “inside story of the making of the smash-hit movie starring Brad Pitt.”

People drew analogies between the Tsarnaevs and such varied siblings as the twins in the David Cronenberg film “Dead Ringers,” the title characters in Dostoyevsky’s “The Brothers Karamazov,” and the Corleones in “The Godfather.”

A Twitter message posted by Dzhokhar Tsarnaev hours after the marathon bombings (“Ain’t no love in the heart of the city, stay safe people”), prompted some amateur detectives to wonder if that reference to Jay-Z’s song “Heart of the City (Ain’t No Love)”) is a direct allusion to 9/11, since the album containing that song was released on Sept. 11, 2001.

The country has processed the Boston Marathon bombings in different ways from the terrorist attacks of 9/11 — in part because the level of digital sophistication has grown so exponentially since then (in 2001, there was no YouTube, no Facebook, no Twitter).

The social-media droppings the Tsarnaev brothers left behind not only attest to their own immersion in the interactive, electronic world, but they have also provided everyone else with plenty of digital data from which to try to extract patterns and possible meaning — fulfilling that very human need to try to make narrative sense of the tragic and the overwhelming.